The present invention extends the technology incorporated into related U.S. Pat. Nos. 5,761,782; 5,798,600; 5,889,354; and 5,892,314. In each of these patents the piezoelectric material illustrating the inventions therein was a multilayer film of polyvinylidene fluoride (PVDF).
Piezoelectric materials have been used extensively as sensors and acoustical/electric coupling devices. Materials that have been used in these devices are made from films of polymer such as polyvinylidene fluoride (PVDF) which are drawn or stretched while subjecting the polymer film to an electric field. The piezoelectric film will then respond to applied electrical fields by either lengthening or shortening depending upon the direction of the applied field.
In the prior art there are several specific techniques disclosed for making the sensor-elements using piezoelectric films; however, common to those folding the piezoelectric polymer film in multi-layers is the use of an epoxy resin or a glue as an adhesive between film layers. Papers disclosing making sensors using bimorph elements and specific techniques in making the elements are: "Application of PVF.sub.2 Bimorph Cantilever Elements to Display Devices", M. Toda and S. Osaka, Proceeding of the S.I.D., Vol 19/2, Second Quarter 1978, pp 35-41; "Electro-motional Device Using PVF.sub.2 Multilayer Bimorph", M. Toda and S. Osaka, Transactions of the IECE of Japan, Vol E61 No 7, July 1978, pp 507-512; "Theory of Air Flow Generation By a Resonant Type PVF.sub.2 Bimorph Cantilever Vibrator", M. Toda, Piezoelectrics, 1979, Vol 22, pp 911-918; "Voltage-Induced Large Amplitude Bending Device--PVF.sub.2 Bimorph--Its Properties and Applications", M. Toda, Piezoelectrics, 1981, Vol 32, pp127-133; and "The Potential of Corrugated PVDF Bimorphs for Actuation and Sensing", Gale E. Nevil, Jr. and Alan F. Davis, SME Conference--Robotics Research: The Next Five Years and Beyond, Aug. 14-16, 1984, Technical Paper MS84-491. When multi-layer piezoelectric polymer film elements were made "the films were bounded together using epoxi-resin (High Super, Cemedine Corp.)" {"Electromotional Devices Using PVF.sub.2 Multilayer Bimorph" ,sic. p 509}.
The following patents are all patents of Toda et al. which disclose bimorph elements of piezoelectric materials. U.S. Pat. No. 4,162,511 discloses a pickup cartridge for use in a velocity correction system which includes a polymer bimorph element mechanically interposed between a cartridge housing and a pickup arm carrying a groove-riding stylus. U.S. Pat. No. 4,164,756 discloses a signal pickup stylus which cooperates with an information storing spiral groove on a video disc record which is caused to selectively skip groove convolutions of the disc record to produce special effects. U.S. Pat. No. 4,176,378 discloses a pickup arm pivotally coupled to a housing support at one end thereof and which is coupled to the housing near its other end by means of bimorph elements attached together at right angles. U.S. Pat. No. 4,234,245 discloses a light control device which includes a bimorph element comprising two thin polyvinylidene fluoride films and a thin layer disposed therebetween to secure the films together. U.S. Pat. No. 4,351,192 discloses a piezoelectric, acoustic vibration detecting element which is positioned in a fluid flow to be measured so as to be moved according to the intensity of the fluid flow away from a source of acoustic vibration. U.S. Pat. No. 4,417,169 discloses a photoelectric circuit arrangement for driving a piezoelectric bimorph element to bend and thereby to open or close a window blind according to the quantity of transmitted light through the blind.
U.S. Pat. No. 4,342,936 discloses a piezoelectric flexure mode device (called a "unimorph") comprising a layer of piezoelectric active material bonded to a layer of piezoelectric inactive material.
U.S. Pat. No. 4,405,402 discloses a thick piezoelectric/pyroelectric element made from polarized plastics such as polyvinylidene fluoride.
U.S. Pat. No. 4,670,074 discloses a composite co-laminated piezoelectric transducer with at least one layer of polymeric substance capable of acquiring piezoelectric properties when co-laminated in the presence of an electric field.
U.S. Pat. No. 4,708,600 discloses a piezoelectric fluid pumping apparatus which includes a pumping apparatus incorporating a piezoelectric energizer.
U.S. Pat. No. 4,939,405 discloses a pump comprised of a piezoelectric vibrator mounted in a casing.
U.S. Pat. No. 5,113,566 discloses a method of producing a multilayer piezoelectric element.